1. Field of the Invention
The invention concerns a lift mechanism for transferring a load between laterally adjacent supporting surfaces at different elevations, especially for moving a load in either direction between a vehicle compartment and the ground alongside the vehicle. The lift mechanism permits different relative motions which are effected alternately or successively when stowing, deploying and moving a platform that supports the load, especially a wheelchair, to be moved back and forth between the passenger compartment of a vehicle such as a van, bus or light truck, and the ground adjacent to such vehicle.
The lift has a substantially vertical fixed frame rigidly mounted to span a vehicle doorway. A partial frame is mounted to move up and down relative to the fixed frame. The partial frame is engaged with the fixed frame when the partial frame is in the upper or retracted position, namely via interengaging protruding and receptacle members at each corner of the fixed and partial frames, which interengaging members position the partial frame relative to the fixed frame and mechanically support the partial frame on the fixed frame. The pivoting frame supports a platform and has vertical and horizontal pivot axes whereby a movable platform can swing into or out of the plane of the doorway on a vertical hinge axis; and the platform can be shifted on a horizontal pivot axis between a vertical stowed position and a horizontal deployed position in which the platform can support a wheel chair or the like.
Using the foregoing frames and hinging or pivoting mountings, the whole lift mechanism can be retracted into a substantially vertical position in which the platform is pivoted up and resides in the doorway. The partial frame can be moved up and down from the doorway, carrying along the pivot frame and platform. When the platform is pivoted up, the pivot frame can be hinged open or shut on the vertical axis. When the pivot frame is hinged shut on the vertical axis the platform can be pivoted down into its horizontal supporting position. These superimposed degrees of freedom of motion are possible because the pivoting frame is carried on a very substantial vertical hinge post, and the partial frame is mechanically engaged in, and partially supported by the fixed frame when raised into the retracted position. The lift thus comprises portions that can be can be hinged open vertically to clear the doorway for passing into and out of the vehicle through an open doorway, or hinged closed across the doorway. The lift further comprises a platform that pivots down to provide a wheel chair support or up for compact stowing. With the platform pivoted down to the supporting position, the partial frame can lift or lower the platform on linkages. The platform thereby raises a wheel chair supported on the platform to the elevation of the vehicle interior floor, or lowers a wheel chair supported on the platform from the vehicle floor to the ground.
The pivoting frame is carried on the partial frame and the partial frame is carried on a parallelogram linkage for guiding the partial frame up or down through an arc, while holding the partial frame parallel to the fixed frame in the doorway. This partial frame supports a platform that is pivotally coupled to the partial frame on a horizontal pivot axis. The platform is pivoted on the horizontal axis to an orientation parallel to the ground and perpendicular to the partial frame, when supporting a load such as the wheelchair. The platform is movable with the partial frame on the parallelogram linkage, from the vehicle compartment level to the ground level, being kept horizontal by the parallelogram linkage. Roll-off gates, barriers and hand holds are provided for safety.
In the reverse order, the platform can transfer a wheelchair from the ground level to the vehicle compartment, whereupon the safety gates and barriers permit the wheelchair to roll into the vehicle. The platform is pivoted up on the horizontal axis, thus moving each of the platform, the partial frame and the pivoting frame into the plane of the fixed frame for compact storage. In this position the mechanism, except for the fixed frame and partial frame, can be unlatched and pivoted clear of the doorway opening.
Accordingly the apparatus has at least three distinct modes of movement. In one mode, the parallelogram linkage holds the platform in a horizontal orientation as the platform is raised or lowered between ground level and the level of the vehicle passenger compartment, opening the movable gates or barriers to permit the wheelchair to roll onto and off of the platform at either level.
In a second mode, the platform is pivotable on a horizontal axis with the movable chassis (i.e., the partial frame) on the inboard side of the platform. The platform can be pivoted on this axis and raised from its horizontal wheelchair-carrying orientation to a vertical orientation. With the platform vertical and the movable chassis retracted, the elements of the mechanism are substantially coplanar with the doorway and the fixed frame. Thus the entire mechanism resides across the vehicle doorway.
The platform is mounted on the movable vertical chassis members by a heavy duty journal post on one lateral side and by a heavy duty clamping latch on the other lateral side. By opening the clamping latch the platform (preferably as folded upwardly into its stowed position), the platform can be swung, in a third mode, clear of the doorway in the manner of a hinged gate frame.
The movable roll-off gates, handrail members and doorway plane barriers for safety purposes preferably are linked and structured for automatic deployment when the platform is in the position where such gates, members and barriers are useful, and for retraction otherwise. For this purpose the handrail members and doorway plane barriers preferably are coupled mechanically to the platform and the parallelogram linkage, respectively. A roll-off gate is provided at each opposite side of the platform. On the inboard side the gate is lowered by a roller contacting the base of the fixed frame at the sill of the vehicle doorway and comprises a transition ramp that is lowered against the base of the fixed frame as the gate is lowered. On the outboard side a similar roller lowers the opposite gate when contact is made with the ground. At least on the outboard side a position latch captures the gate mechanism until lifted by contact between the roller and the ground. As a result, the roll-off gate cannot be opened inadvertently by rolling the wheelchair against it when the platform is not on the ground.
More particularly, a mounting structure having laterally-spaced fixed vertical posts is rigidly mounted in the vehicle doorway, inside the innermost (closed) position of the vehicle outer door, leaving clearance for the outer door hinges and latch mechanism. The fixed vertical posts preferably extend from the vehicle floor to the roof. An upper horizontal header and a lower horizontal base or sill are disposed around the doorway or a portion of the doorway, and frame the doorway together with the vertical posts. The laterally spaced vertical standards of the movable chassis are attached to the fixed posts by a parallelogram linkage, namely at least two parallel pivot arms pivotally affixed to the fixed posts and vertical standards such that the standards remain parallel to the fixed posts. Preferably such a parallelogram linkage is provided at each lateral side of the lift.
The movable standards reside against the fixed posts in the retracted position of the lift. The parallelogram linkage collapses when the standards are retracted inboard and opens when the standards are deployed outwardly and downwardly to lower the lift. In this manner the parallelogram linkage(s) keep the movable standards parallel to the fixed frame (substantially vertical) and keep the wheel chair supporting platform horizontally oriented when deployed.
The platform is attached to the movable vertical standards on a horizontal hinge axis extending between the standards adjacent their lower ends. The platform can be pivoted up into a vertical position, substantially in the plane of the standards, where the platform is stowed in a position comparable to a door panel, or positioned horizontally to support the wheelchair or other load. A drive device such as a linear actuator motor is provided for this purpose. The movable standards are connected to the fixed posts by a set of parallelogram arms. Hinging on the horizontal axis can be effected manually, but a drive powered by an electric linear actuator is preferred. Independent pivoting of the platform on a vertical hinge axis permits the vertically stowed platform to be pivoted clear of the doorway around one of the movable vertical standards.
The vertical hinge axis is defined by one or more heavy journal posts, as needed to support the weight of the platform when hinged open. At the same time, the movable standards are engaged with and supported on the fixed posts, forming a stable structure from which the platform can hinge on the journal post, without sagging. A particularly robust and secure clamped latch arrangement is provided between the platform and the adjacent movable vertical standard on the side opposite from the vertical hinge. The clamped latch comprises a leveraged operator that fixes a protruding bar adjacent to the horizontal pivot axis of the platform, received in a structurally supportive receptacle coupled to the vertical movable frame. The journal post and clamping latch bear the concentrated load of a wheel chair on the platform when cantilevered outwardly.
2. Prior Art
U.S. Pat. No. 4,664,584--Braun et al. discloses a wheelchair lift for a van, having a horizontal platform mounted to a telescoping drive post carrying a hydraulic actuator for moving the horizontal platform vertically up and down between the ground and the level of the floor of the passenger compartment. The apparatus is attached to the floor of the van and is mounted inside a side door. The movable parts of the lift, namely the platform and the vertical drive post, hinge on a vertical axis. The entire lift is mounted inside the van at the edge of the doorway. For disembarking, the wheelchair is rolled onto the platform inside the van; the platform is rotated outwardly around the vertical pivot post to move the telescoping post and platform outward sufficiently to clear the passenger compartment; the platform is lowered to the ground; and the wheelchair is rolled off. For embarking the opposite steps are taken.
A lift as in Braun is mounted such that all the elements of the lift can be moved completely inside the vehicle, allowing the door to be closed. When the door is open, the device extends a portion outwards and lowers it, both typically by means of actuators. It is an inherent aspect of a device as described that the vertically displaceable platform or similar load carrying part, and also the mechanism that raises and lowers it (i.e., the telescoping post), must be movable fully outside of the vehicle doorway to provide clearance to lower the platform to the ground. These elements must also be movable entirely inside of the passenger compartment, by linear retraction and/or pivoting, which cause a large cause the mechanism to occupy floor space in the vehicle passenger compartment.
The platform and vertical drive in Braun can hinge or pivot through 90.degree.. The platform remains horizontal, as necessary to support a wheelchair. When the platform is inside the van the wheelchair is rolled Ont. (or off of) the platform, for example in a direction perpendicular to the longitudinal axis of the vehicle. When the platform is outside the van, the user moves on or off the platform in a direction parallel to the longitudinal axis of the vehicle. This arrangement is effective for moving the vertically displaceable parts of the lift through the van doorway in either direction, with clearance when outside. However, in addition to occupying a good deal of space in the van, the mechanism blocks the doorway. Whether deployed or stowed, the mechanism and its rotational and vertical path require persons without wheelchairs to maneuver over or around the platform to pass through the doorway in a normal ambulatory manner.
Another form of wheelchair lift for a van is disclosed in U.S. Pat. No. 4,353,436--Rice et al. According to this arrangement, a linearly displaceable track and roller arrangement moves two vertically telescoping drive posts on opposite sides of the vehicle doorway, into the van or out of the van. When the drive posts are clear of the doorway, the platform can be lowered.
In U.S. Pat. No. 5,542,811--Vartanian, which is commonly owned with the present application, a wheelchair lift is mounted in a vehicle at one side of the doorway, for example at the front frame of a sliding side door of a van. A platform is positionable horizontally for carrying a wheelchair to be moved into or out of the vehicle. A vertical drive mechanism is attached to the platform at a corner adjacent the vehicle doorway, and has a hydraulic cylinder and chain drive raising and lowering the wheelchair relative to the doorway. A base member is attached to the vehicle inside the doorway on the floor. A carriage is carried on the base member for linear movement toward and away from the doorway. The vertical drive mechanism is coupled to the carriage on a vertical hinge or pivot axis that is movable by a linear actuator from a position at which the hinge axis is inside the vehicle to a position outside of the vehicle clear of the doorway. The platform can be raised, lowered and rotated on the vertical pivot axis. Since linear movement rather than rotation clears the doorway, a wheelchair occupant can move on or off the platform from a number of angles of approach between parallel to the longitudinal axis of the vehicle and perpendicular thereto. This device must be securely affixed to the vehicle to provide adequate strength without wobbling, particularly because the structure cantilevers the weight of the wheelchair and occupant relative to the base where it attaches to the vehicle. This device also substantially occupies the doorway and interferes with ambulatory passage.
Other wheelchair access assists are disclosed in U.S. Pat. Nos. 4,966,516 and 5,085,555--Vartanian. These devices involve segmented ramps that are folded in segments for stowing, or are unfolded for wheelchair access. The ramps are not powered and the assistance of a party on the ground is needed to deploy and to stow the ramp. To clear the doorway for a person to walk through, the '516 patent comprises means for pivoting the folded platform on a vertical axis in the manner of a gate. Whereas the structure used for rolling into or out of the vehicle is a simple and relatively lightweight folded ramp, the hinge structure need only support the weight of the two ramp segments. These segments are made of a relatively light openwork grid structure, and when the ramp is extended the segments are supported on the ground and on the sill of the doorway, rather than on the hinging structure. Additionally, the latching arrangement operates only as a gate latch that prevents the segments from hinging or swinging open, and does not support their weight.
U.S. Pat. No. 5,261,779--Goodrich discloses a powered platform arrangement that does not pivot clear of the doorway, but is lifted into position in the doorway or lowered to the ground by a parallelogram linkage that holds two carrying arms in a vertical position. The platform is pivoted on a horizontal axis to the vertical arms. As in certain of the foregoing known lifts, the device is heavy and complicated, or cannot be used or stowed compactly, or interferes with free access through the doorway for unassisted passage of the wheelchair occupant.
It would be advantageous to provide a wheelchair lift structure that has many of the advantages that are achieved individually in one or more of the foregoing patents. However each of the prior art structures achieves the advantages at the cost of corresponding drawbacks, and it has not been shown how one might achieve all the advantages in one structure. It would be particularly advantageous, for example, to provide a compact wheelchair lift that does not use a great deal of interior space, can be moved clear of the doorway, that positions the load in a cantilevered manner rather than on a long ramp, that can be used unattended by a wheelchair occupant, and that is durable in its structure, attachment and use.